"""
@name : 2
@author : wangaokang
@projectname: pythonProject4
"""
print('请输入PM2.5的值：')
while (1):
    a = input()
    if a == 'Q':
        print('退出循环')
        break
    elif int(a)<=50:
        print('优')
    elif int(a)>50 and int(a)<=100:
        print('良')
    elif int(a)>100 and int(a)<=150:
        print('轻度污染')
    elif int(a)>150 and int(a)<=200:
        print('中度污染')
    elif int(a)>200 and int(a)<=300:
        print('重度污染')
    elif int(a)>300:
        print("严重污染")
